Auto-Zeroing Resonator Oscillator for Low Near-Phase Noise
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Solution Overview
Problem
Resonator-based oscillators suffer from high 1/f noise corner frequencies, leading to significant near-phase noise, which conventional technologies have not effectively mitigated.
Innovation Solution
The implementation of auto-zeroing sustaining amplifiers with active offset cancellation, utilizing control signals ϕ1 and ϕ2 to synchronize and zero the amplifier offset during resonator cycles, significantly reducing the 1/f noise corner frequency to below 10 Hz or 1 Hz, thereby reducing near-phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sustaining amplifiers are used in resonator-based oscillators, then the oscillator can maintain continuous operation, but the 1/f noise corner frequency remains high leading to significant near-phase noise
Solution Approach 1:
The patent applies preliminary action by performing offset cancellation before the offset can significantly degrade performance. The sustaining amplifier offset is measured and cancelled in advance during a calibration phase, so that when the oscillator operates, the harmful offset is already minimized. This is achieved through a test mode that measures the amplifier offset and stores compensation values for use during normal operation.
Solution Approach 2:
The patent implements feedback by continuously monitoring the sustaining amplifier offset and applying corrective action. A feedback loop measures the actual offset of the amplifier and adjusts the drive signal accordingly to compensate for the offset. This closed-loop approach ensures that the harmful offset is actively counteracted, reducing near-phase noise while maintaining continuous operation.
2Device complexity
If amplifier offset is not cancelled, then the oscillator circuit remains simple, but the 1/f noise corner frequency is high causing degraded timing signal quality
Solution Approach 1:
The patent applies segmentation by dividing the oscillator operation into distinct functional segments: a test mode for measuring and characterizing amplifier offset, and a normal operation mode for generating timing signals. This segmentation allows the complex offset cancellation functionality to be isolated and activated only when needed, rather than requiring continuous complex circuitry during normal operation. The timing signal generator is thus segmented into measurement and generation functions.
Solution Approach 2:
The patent changes operational parameters by switching between different operating modes (test mode and normal operation mode) with different parameter settings. During test mode, the system uses parameters optimized for measuring amplifier characteristics, while during normal operation, it uses parameters optimized for timing signal generation with pre-applied offset compensation. This parameter changing approach allows high timing signal quality without permanently complex circuitry.
Data Source
AI summary
An oscillator includes a resonator, sustaining circuit and detector circuit. The sustaining circuit receives a sense signal indicative of mechanically resonant motion of the resonator generates an amplified output signal in response. The detector circuit asserts, at a predetermined phase of the amplified output signal, one or more control signals that enable an offset-reducing operation with respect to the sustaining amplifier circuit.